Stabilize unused-unpacked-variable (RUF059) (#20233)

The tests looked good. For the docs, I added a `## See also` section
pointing to
the closely-related F841 (unused-variable) and the corresponding section
to F841
pointing back to RUF059. It seems like you'd probably want both of these
active
or at least to know about the other when reading the docs.

crates/ruff_linter/src/codes.rs

@@ -1046,7 +1046,7 @@ pub fn code_to_rule(linter: Linter, code: &str) -> Option<(RuleGroup, Rule)> {
         (Ruff, "056") => (RuleGroup::Preview, rules::ruff::rules::FalsyDictGetFallback),
         (Ruff, "057") => (RuleGroup::Stable, rules::ruff::rules::UnnecessaryRound),
         (Ruff, "058") => (RuleGroup::Stable, rules::ruff::rules::StarmapZip),
-        (Ruff, "059") => (RuleGroup::Preview, rules::ruff::rules::UnusedUnpackedVariable),
+        (Ruff, "059") => (RuleGroup::Stable, rules::ruff::rules::UnusedUnpackedVariable),
         (Ruff, "060") => (RuleGroup::Preview, rules::ruff::rules::InEmptyCollection),
         (Ruff, "061") => (RuleGroup::Preview, rules::ruff::rules::LegacyFormPytestRaises),
         (Ruff, "063") => (RuleGroup::Preview, rules::ruff::rules::AccessAnnotationsFromClassDict),

crates/ruff_linter/src/message/snapshots/ruff_linter__message__sarif__tests__results.snap

@@ -119,7 +119,7 @@ expression: value
             },
             {
               "fullDescription": {
-                "text": "## What it does\nChecks for the presence of unused variables in function scopes.\n\n## Why is this bad?\nA variable that is defined but not used is likely a mistake, and should\nbe removed to avoid confusion.\n\nIf a variable is intentionally defined-but-not-used, it should be\nprefixed with an underscore, or some other value that adheres to the\n[`lint.dummy-variable-rgx`] pattern.\n\n## Example\n```python\ndef foo():\n    x = 1\n    y = 2\n    return x\n```\n\nUse instead:\n```python\ndef foo():\n    x = 1\n    return x\n```\n\n## Fix safety\n\nThis rule's fix is marked as unsafe because removing an unused variable assignment may\ndelete comments that are attached to the assignment.\n\n## Options\n- `lint.dummy-variable-rgx`\n"
+                "text": "## What it does\nChecks for the presence of unused variables in function scopes.\n\n## Why is this bad?\nA variable that is defined but not used is likely a mistake, and should\nbe removed to avoid confusion.\n\nIf a variable is intentionally defined-but-not-used, it should be\nprefixed with an underscore, or some other value that adheres to the\n[`lint.dummy-variable-rgx`] pattern.\n\n## Example\n```python\ndef foo():\n    x = 1\n    y = 2\n    return x\n```\n\nUse instead:\n```python\ndef foo():\n    x = 1\n    return x\n```\n\n## Fix safety\n\nThis rule's fix is marked as unsafe because removing an unused variable assignment may\ndelete comments that are attached to the assignment.\n\n## See also\n\nThis rule does not apply to bindings in unpacked assignments (e.g. `x, y = 1, 2`). See\n[`unused-unpacked-variable`][RUF059] for this case.\n\n## Options\n- `lint.dummy-variable-rgx`\n\n[RUF059]: https://docs.astral.sh/ruff/rules/unused-unpacked-variable/\n"
               },
               "help": {
                 "text": "Local variable `{name}` is assigned to but never used"

crates/ruff_linter/src/rules/pyflakes/rules/unused_variable.rs

@@ -43,8 +43,15 @@ use crate::{Edit, Fix, FixAvailability, Violation};
 /// This rule's fix is marked as unsafe because removing an unused variable assignment may
 /// delete comments that are attached to the assignment.
 ///
+/// ## See also
+///
+/// This rule does not apply to bindings in unpacked assignments (e.g. `x, y = 1, 2`). See
+/// [`unused-unpacked-variable`][RUF059] for this case.
+///
 /// ## Options
 /// - `lint.dummy-variable-rgx`
+///
+/// [RUF059]: https://docs.astral.sh/ruff/rules/unused-unpacked-variable/
 #[derive(ViolationMetadata)]
 pub(crate) struct UnusedVariable {
     pub name: String,

crates/ruff_linter/src/rules/ruff/rules/unused_unpacked_variable.rs

@@ -36,8 +36,15 @@ use crate::{Edit, Fix, FixAvailability, Violation};
 ///     return x
 /// ```
 ///
+/// ## See also
+///
+/// This rule applies only to unpacked assignments. For regular assignments, see
+/// [`unused-variable`][F841].
+///
 /// ## Options
 /// - `lint.dummy-variable-rgx`
+///
+/// [F841]: https://docs.astral.sh/ruff/rules/unused-variable/
 #[derive(ViolationMetadata)]
 pub(crate) struct UnusedUnpackedVariable {
     pub name: String,